1. Field of the Invention
The present invention relates to an automotive safety device which, upon the onset of a collision, deploys an inflatable restraint cushion, commonly known as an air bag cushion, so as to provide impact protection to occupants of the passenger vehicles. More particularly, this invention relates to a device for protecting the upper portion of the air bag cushion from hot gases generated during the deployment of the air bag cushion.
2. Description of Related Art
An air bag restraint system, referred to as a module, typically includes a canister which encloses a gas generator or, as it is commonly known, an inflator, and at least part of an air bag cushion, and a cover which conceals the module from view. When the vehicle is involved in a collision, a crash signal initiates operation of the inflator to cause the air bag cushion to deploy. The inflator produces an inert gas (e.g., nitrogen) which is directed under pressure into the air bag cushion to force it out of the canister incorporated into the module and into the passenger compartment of the vehicle. In a pyrotechnic-type inflator, gas is produced by the burning of a gas generating material. As the air bag cushion is forced out of the container, pressure exerted on the cover causes selected portions of the cover to separate in a predetermined manner along tear seams to enable the air bag cushion to be directed into the passenger compartment. As the air bag cushion is directed into the passenger compartment, it is inflated by the continued flow of gas produced by the inflator. One possible location for an air bag assembly is in the instrument panel or dashboard on the passenger side of the vehicle.
An air bag cushion is normally made from a synthetic material that is substantially impermeable to the flow of gas. During the early stages of the air bag cushion deployment, prior to the air bag cushion rupturing the tear seams of the cover, the inflator generates a large volume of hot gases under high pressure. The hot gases exiting from the inflator impinge on the top section and the side sections adjacent to the gas inlet opening of the air bag cushion. Normally, the air bag cushion is spaced a sufficient distance from the inflator that the hot gases do not affect the strength of the air bag cushion. However, when a more energetic deployment takes place the hot gases generated by the inflator may structurally affect the air bag cushion. Further, upon completion of the air bag cushion deployment, the air bag cushion collapses and falls onto or into the canister such that the fabric from which the cushion is made may come within close proximity to the hot inflator. It would be preferable to have a device that protects the air bag cushion from the hot deployment gases, while not inhibiting the operation of the inflator or air bag cushion during the deployment process. Further, it would be desirable to protect the air bag cushion from the heat emanating from the hot inflator after the deployment process has been completed.
Solutions to these problems have been accomplished by linings in the air bag cushion or diverters which redirect the flow of gas from the inflator. Such prior art solutions are disclosed in Acs, U.S. Pat. No. 3,214,458; Bishop el al., U.S. Pat. No. 4,944,527; Wooley et al., U.S. Pat. No. 5,149,130; and Fischer et al., U.S. Pat. No. 5,160,164.
Acs recites a combined heat and energy absorbing bag within the air bag cushion. The inner bag is in the form of a fiberglass bag that is expandable, but not stretchable, low porosity bag. The inner bag provides limitations to the overall air bag cushions. These limitations may not be acceptable in all air bag cushion designs.
Bishop recites a retainer in the form of a metal sheet having a set of U-shaped slots formed therein. When the metal sheet is formed into an open-ended cylinder the metal within the slots extends from the cylinder to form a heat shield. The inflator is inserted into the open-ended cylinder and the assembly is installed into the canister. This shield provides protection to the air bag cushion immediately adjacent to the inflator, however, that part of the air bag cushion extending beyond the canister may not protected from hot gases produced by an energetic inflator.
Wooley recites a heat resistive fabric liner interposed between a heat shield chamber containing a pyrotechnic inflator and the base of the air bag cushion. Alternatively, the base of the air bag cushion may be formed from a heat resistive fabric. The heat resistive liner or bag section protects the base of the air bag cushion from heat conducted from the inflator after the cushion has been deployed, however, the liner does not protect that portion of the cushion covering the air bag canister from hot gases generated during deployment.
Fischer recites a deflector, which is made from the same material as the air bag cushion, that redirects the flow of gas from the inflator so that the initial contact between the air bag cushion and a vehicle occupant is at the occupant's torso. Such modification of the deployment may not always be beneficial. Further, the deflector may not reposition itself after deployment is complete to cover the inflator and protect the air bag cushion from post deployment burn through.